As Trump continues to hold out the threat of declaring a national emergency to abscond with the funds he wants to build his nonsensical wall, there’s one factor that hasn’t gotten a lot of attention: As soon as Trump declares an emergency, Nancy Pelosi can force a vote over whether or not that emergency continues.

On Thursday evening, Donald Trump was “definite” about his intention to declare a national emergency, and through Friday, Senate-hating Senators such as Lindsey Graham have been cheering on the idea of government by fiat. However, through the day on Friday, there have been signs that some Republicans are actually passing the word that they’re not all that thrilled with this idea, and Trump’s attorneys have made it clear to him that an attempt to sidestep the constitutional roles of Congress and the executive will result in a swift trip to court.

And there’s another possibility. The National Emergency Act contains provisions that allow either the House or the Senate to produce a resolution to end an emergency declaration. In fact, the law sets a maximum period of six months before the Senate and House must vote on the continuation of an emergency—but it sets no minimum. If Donald Trump actually does declare a national emergency, Pelosi doesn’t have to wait six months. She doesn’t have to wait six minutes. She can immediately call a vote in the House ordering the end of that emergency.

That resolution would then move to the Senate. And it would have to get a vote.

Such a joint resolution passed by one House shall be referred to the appropriate committee of the other House and shall be reported out by such committee together within its recommendations within fifteen calendar days.